In water treatment systems it is well known to inject de-contaminating agents such as for example gaseous chlorine into the water in order to meet certain standards for the purity of the water.
From the prior art it is known to provide automatic flow control for fluids for example by means of a fluid control proportional valve as shown in U.S. Pat. No. 4,790,345. This valve, however, lacks several features required for a water and waste water chlorinating system as disclosed in more detail in the present application.